Help Me Get My T18 Clutch Released!

I ordered a 15501 Lakewood. Whats weird is that the fork angle setup is per Novak instruction and a little forward facing (I forget the angle but it is whatever they spec). The fork is also in the front 1/3 or 1/2 of the window too. And the fork moves the entire range of the cable pull motion...it just that the motion it moves isn't far back enough. Now just to figure out how much to adjust this one. Is the GM 3790556 the one thats 1 1/8" from threads up to end of the ball stud? Do we know if that length is where I should be with my adjustable one?

My bearing retainer came this morning. I turned down and shortened it to gm spec. I removed my pivot ball from the bellhousing, installed my clutch and dry fit the transmission. For any curious followers, parts are Dauntless 52lb flywheel, LUK 01015 clutch kit, release bearing CC1705C (21/32 fork to finger length), and of course a short input t-18.
It looks like I have about 1/8" clearance which should allow plenty of non contact in all situations.
Next I will install the clutch fork, ball stud and test for clutch release.

Here is a better shot of the release bearing clearance. With the bearing pushed to the clutch fingers, you can see the clearance between the bearing retainer and release bearing. It is slightly less than 1/8" as I cannot get a 1/8" thick ruler to slide in between. Does anyone know just how much these raised finger clutches need to be depressed in order to release?
After playing with my entire setup assembled on the floor, it looks to me that my stock length pivot ball should give me plenty of travel.

"The C2/C3 Corvettes (and most GM passenger cars) have a total movement range at the throwout bearing, when the clutch pedal is depressed its full stroke, of about .580” (just over 9/16”). That means that you have to use a pressure plate that fully disengages the clutch with about ½” of pressure plate diaphragm movement. Full clutch disengagement is considered to be a .050” gap between the pressure plate and the clutch disc."

"With the clutch, pressure plate, and the flywheel removed from the vehicle, I re-assembled the clutch and pressure plate to the loose flywheel. This assembly was then placed in a hydraulic press with the throwout bearing in place, and a dial indicator gauge was placed on the throwout bearing to measure its total stroke against the pressure plate.

The bearing was compressed .100” at a time: At .100, the clutch was locked in there solid. No change at .200, .300, .400, or .500. At the .500 distance, the disc should have been loose, with the .050” spec clearance. But it was locked solid. At .650 the disc just barely came loose, and it hit the required disengagement spec of .050” at a total bearing travel of .780” ."

I am going to assemble trans, bell, clutch fork and release bearing here on the floor. I can then see how much travel I achieve.
To the OP, Are you sure that your input shaft isnt bottoming out on the pilot bushing? Or perhaps your clutch fork is different being from the long bellhousing 71?

Yeah I am sure nothing is bottoming out. I have many loose inputs and 3 machined retainers here. I did not put my combo in my press but using a ratchet strap to the rear axle I got it to disengage with the fork arm to the back of the hole in the bellhousing. I bought a new arm for a 69 and its the same as the stock 71 arm. I think in my case the only way I'll be able to get my given pedal throw to work with this clutch is to get the fork arm to travel back further and I can't imagine another way to do it but for the adjustable ball. In your case it looks like it might be worth just putting together and testing. Worst case you pull it apart and swap the ball to your long version. I wish I had my pivot ball here to measure so we could compare...I'm not sure if my pivot is different from yours but everything else we have is identical.

Thats a good link on the corvette forum...if I find time I might put my combo in my press just to see if I releases in a distance I think my pedal throw can work with. My only other option is get a new Luk pressure plate that is original to the Jeep. It seems like a good idea to run the disk we have with a stock Jeep V6 pressure plate and longer bearing to compensate for the stock flat finger diaphragm. Any reason to run the pressure plates we have?

Yeah I am sure nothing is bottoming out. I have many loose inputs and 3 machined retainers here. I did not put my combo in my press but using a ratchet strap to the rear axle I got it to disengage with the fork arm to the back of the hole in the bellhousing. I bought a new arm for a 69 and its the same as the stock 71 arm. I think in my case the only way I'll be able to get my given pedal throw to work with this clutch is to get the fork arm to travel back further and I can't imagine another way to do it but for the adjustable ball. In your case it looks like it might be worth just putting together and testing. Worst case you pull it apart and swap the ball to your long version. I wish I had my pivot ball here to measure so we could compare...I'm not sure if my pivot is different from yours but everything else we have is identical.

Click to expand...

My pivot ball measures 1 1/2" over all length.
I just came in from dry assembling my combo. Before installing I checked the release bearing face distance and found that I get 1" of travel out of the release bearing before the clutch fork hits the back of the bellhousing window. From there we installed the trans, bell all in one. At about 1/2" of release bearing travel the transmission output is barley turn able by hand and you can hear it dragging on both the flywheel and pressure plate. Around 3/4" of travel you no longer hear the pressure plate drag and the flywheel drag is of course minimal. The trans output is also easy to turn at this point. That 3/4" of release bearing travel is close to bottom of the pedal travel. Letting the pedal out the clutch starts grabbing just before hitting half pedal. Keep in mind I am turning the trans output by hand which is no where near as powerful as the engine would be. The clutch is releasing long before the arm would hit the back of the bellhousing window.
I did notice that this clutch is harder to push than the old one. I am hoping that it is due to a lack of grease, stiff pressure plate and I am using a new clutch fork that feels really tight on the release bearing. I may dress the fork opening with a file a little bit as the bearing doesn't seem to pivot on the fork freely.
I need to modify my clutch cable setup a little bit, as it is too short to allow the release bearing to completely back off the fingers. Way back I shortened the threads on the cable to accommodate my old setup. Time to make an extension I guess.

Place the pressure plate on it's fingers and lay the clutch disc on top. Place a flat edge across the disc and PP and measure the distance in the gap from top of disc to bolt mounting flange on PP. This tells you the distance of travel required by the T/O bearing to release the disc.

I noticed a heavy pedal too when I was testing. It begs the question: why use a pressure plate that is any different from the OEM dauntless diaphram pressure plate? If the new disk is combined with an OEM Dauntless pressure plate (flat fingers), couldn't we run the rounded face throwout bearing and keep the softer oem pedal feel?

I noticed a heavy pedal too when I was testing. It begs the question: why use a pressure plate that is any different from the OEM dauntless diaphram pressure plate? If the new disk is combined with an OEM Dauntless pressure plate (flat fingers), couldn't we run the rounded face throwout bearing and keep the softer oem pedal feel?

Click to expand...

I think you could do that, but I still think you might need the longer pivot stud in order to get enough travel. I wonder if the increased clutch fork angle would lower pedal effort?

When it comes to my old clutch I don’t have any idea of its history. It was flat finger, old and visually abused. It was softer than this one.
I have the long, 1 7/8” release bearing on the bench, I’m tempted to buy a flat finger pressure plate and try it.

One more fly for the soup, I have read that the replacement throw out arms need ground out so they don’t bind. Mine when bench testing does not pivot smoothly on the release bearing.

I'll bite the bullet and order a Luk clutch set for a Dauntless today. Theres no sense in me reinstalling my old Dauntless pressure plate because if it works well I will want a new pressure plate in there. I'll try the Dauntless pressure plate with the 77 CJ5 304 disk I have and report back. My new fork is actually pretty loose on the release bearing...it doesn't come close to hugging too tight and at first I thought it wouldn't work but when installed with the input bearing retainer (as opposed to holding bearing in the fork) it moves back and forth fine.

The Dauntless setup comes with a curved face throw out that might just be the right height but will check to see if theres an 1/8" of air play in the setup before I proceed. According to Novak site (I missed this before) the typical Jeep pressure plate requires less travel to release than the GM pressure plates. To be honest I am not thrilled with how heavy the current 77 pressure plate is...perhaps because those Jeeps use different leverage on the linkage or possibly are hydraulic? I believe the Jeep pressure plate needs 0.390 to release while the GM needs 0.550. Seems negligible but hopefully the flat finger stock Dauntless will also just be lighter for easier pedal modulation off-road.

One question...my throwout bearing retainers have a hump in the circumference area that attaches into the fork. Where do you place that hump?

I'll bite the bullet and order a Luk clutch set for a Dauntless today. Theres no sense in me reinstalling my old Dauntless pressure plate because if it works well I will want a new pressure plate in there. I'll try the Dauntless pressure plate with the 77 CJ5 304 disk I have and report back. My new fork is actually pretty loose on the release bearing...it doesn't come close to hugging too tight and at first I thought it wouldn't work but when installed with the input bearing retainer (as opposed to holding bearing in the fork) it moves back and forth fine.

The Dauntless setup comes with a curved face throw out that might just be the right height but will check to see if theres an 1/8" of air play in the setup before I proceed. According to Novak site (I missed this before) the typical Jeep pressure plate requires less travel to release than the GM pressure plates. To be honest I am not thrilled with how heavy the current 77 pressure plate is...perhaps because those Jeeps use different leverage on the linkage or possibly are hydraulic? I believe the Jeep pressure plate needs 0.390 to release while the GM needs 0.550. Seems negligible but hopefully the flat finger stock Dauntless will also just be lighter for easier pedal modulation off-road.

One question...my throwout bearing retainers have a hump in the circumference area that attaches into the fork. Where do you place that hump?

Click to expand...

Some have a hump, some have a pin, either way it is there to keep the bearing mount from spinning in the clutch fork. I have it inside the fork.
How far out is your pressure plate? I’m tempted to go with what I have and convert to hydraulic using floor pedals and this Series 320 With Round Master Cylinder - CNC, Inc.
If u install the stock plate and say it’s easier I would go that route.

I don't know how far out my stock plate is but its unmarked and I don't want to reinstall a used pressure plate. I do know that it was originally designed for a cable actuation, didn't slip, and felt so much better than this 77 CJ5 pressure plate. I sorta started dreading my T18 swap when I first felt how heavy the clutch pedal was - if the stock plate works with the disk we have now then we'll be back to soft clutch actuation with sufficient clamping force.

Should have parts Wednesday or Thursday. I will use my ratchet strap trick to see if pulling back on the fork the amount of travel that the cable gives me will release the clutch or not. If not I'll try the longer ball stud.

Here are a couple tidbits and their respective sources that I found today.

Novak: Release Distance Required? Our research shows that a typical GM clutch pressure plate, whether three-finger style or diaphram, 10-1/2" or 11" generally requires 0.550" of travel at the fingers to release the clutch disc. Some common Jeep pressure plates require about 0 390" of travel to release.

Advance Adapters:

Most notably, on the Advance Adapters chart you can see that the GM/Buick, AMC, and Buick 225 10.5" pressure plates are all different part numbers. Under AMC there is a different pressure plate used depending on whether you are mechanical or hydraulic clutch. I have no idea whether the LUK 01015 for the 77 CJ5 V8 is for mechanical or hydraulic actuation. The more I think about it the more it seems a good idea to stick with the stock pressure plate coupled to the 77 CJ5 V8 disk. Lets see what happens when I get it in I guess.